1. Field of the Invention
The present invention relates to a lithography system employing a charged-particle beam such as an electron beam. More particularly, this invention is concerned with a technology for controlling a settlement wait time for each of the amplifiers connected to the main deflectors in a multicolumn charged-particle beam lithography system. Herein, the multicolumn charged-article beam lithography system has a plurality of columns for patterning an exposed sample (specifically a wafer) by deflecting and sweeping an electron beam on the wafer according to exposure pattern data.
2. Description of the Related Art
In recent years, a lithography method employing a charged-particle beam such as an electron beam or ion beam or a novel lithography method employing X rays has been studied and put to practical use. The method is expected to supercede photolithography, which was once the mainstream of fine patterning, due to the trend of producing integrated circuits with higher density elements. An electron-beam lithography system for patterning a wafer using an electron beam is characterized by a better resolution than that offered by a photolithography system. However, the electron-beam lithography system has the drawback of low throughput. For improving throughput, a block lithography method or blanking aperture array (BAA) method has been devised. Aside from these methods, a multicolumn electron-beam lithography system is thought to be effective. If the multicolumn electron-beam lithography system merely has an increased number of columns, it cannot be said that the lithography system gains an advantage over a plurality of conventional mono-column electron-beam lithography systems (for example, the one shown in FIG. 1) placed mutually adjacently. The multicolumn electron-beam lithography system is advantageous from a spatial viewpoint, though. If the multicolumn electron-beam lithography system is designed so that a control unit will be used in common and a pattern to be drawn is the same among the plurality of columns, the lithography system will prove effective.
However, if the columns differ from one to another, when the same signal is supplied to the columns so that the columns will expose wafers to draw the same pattern, a mismatch occurs among the columns. This poses a problem in that exposure cannot be achieved normally. A critical mismatch occurring among the columns is a mismatch among settlement times to be spent by main deflectors. The settlement time to be spent by a main deflector is the time required until a position of deflection to which the main deflector deflects light is modified and settled. The settlement time varies depending on the properties of a main deflector or a difference from a previous position of deflection. A settlement wait time control unit composed of a wait time determining unit and wait time counter is included in association with each column. However, this poses a problem in that the circuit scale of a lithography system expands.
An object of the present invention is to provide a charged-particle beam lithography system having the circuitry of a settlement wait time control unit simplified, and capable of contributing to improvement of efficiency in extending settlement wait time control for an amplifier included in a main deflector. The settlement wait time control unit controls a settlement wait time to be spent by each of amplifiers connected to main deflectors necessary to realize concurrent exposure among columns.
For accomplishing the above object, according to the present invention, there is provided a charged-particle beam lithography system having a plurality of columns for patterning an exposed sample by deflecting and sweeping a charged-particle beam on the exposed sample according to exposure pattern data. The charged-particle beam lithography system further includes a control unit for controlling a settlement wait time to be spent by each of amplifiers connected to main deflectors necessary to realize concurrent exposure among the columns. The control unit includes a circuit for comparing magnitudes of changes in deflection data output from main deflector, adjusting circuits included in the columns with one another and selecting a maximum value. The control unit further includes a circuit for determining a settlement wait time for all the columns according to the magnitude of a change of the selected maximum value.
According to the configuration of the charged-particle beam lithography system of the present invention, after a maximum value is selected from among the magnitudes of changes in deflection data, a settlement wait time is determined for all the columns according to the magnitude of a change of the maximum value. Wasteful counting actions for xe2x80x9cdouble countingxe2x80x9d that are carried out in related arts can be prevented. Moreover, only one circuit for determining the settlement wait time (wait time determining unit) is included in association with the columns. This leads to simple circuitry and contributes greatly to improvement of efficiency in extending settlement wait time control.